The aim of our study was to determine the effectiveness of a program of transcendental meditation aimed at increasing psychological flexibility, reduce stress and gain heart rate variability. The sample was composed of 72 student volunteers and divided into three groups, 20 in the experimental group, who practice meditation with mantra (MT), 29 in the active control group, which learn meditation with breathing (MR) and 23 students part of the waiting group. The intervention lasted six weeks, and the time dedicated to learning the technique: four days at baseline and a session for general information. The dependent variables were: Psychological Flexibility (measured with the acceptance and action questionnaire, AAQII), stress (measured by recovery from stress questionnaire, RESTQ) Rate Heart Variability (laboratory) and Mindfulness (measured trough FFMQ questionnaire). These variables were evaluated initially and after 3 and 6 weeks of continuous meditation, 20 minutes twice a day. The conclusions are that: the TM program is very effective to increase psychological flexibility, reduce stress, enhance recovery and increase full consciousness. The breathing meditation program is also positive but less effective than MT, increasing psychological flexibility, reduces stress, increases recovery and increases full consciousness. The waiting group shows no change during the study period. The effects on heart rate variability are of lesser magnitude.